Global flood risk projection under climate change and shared socioeconomic pathways

Abstract

Climate change and socioeconomic development jointly amplify global flood threats, yet integrated projections remain limited. Here we developed a stacking ensemble framework combining the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model precipitation data with population, economic, and land-use trends under Shared Socioeconomic Pathways (SSPs). This framework is to project global flood risk under climate change. Our results reveal a persistent increase in flood risk index (FRI) throughout the 21st century, with the highest emission scenario (SSP5-8.5) driving a 18.8% rise by 2081–2100 compared to the baseline period (1995-2014). Notably, under the low-emission SSP1-2.6, FRI already increases by 13.1% in the near future (2021–2040)—approximately 70% of the SSP5-8.5 endpoint increase—indicating substantial near-term risk commitment from historical emissions. High-risk areas concentrate in floodplains and coastal zones, with Asia exhibiting the highest median risk and greatest internal heterogeneity. Economic exposure surges disproportionately in high-income and rapidly developing economies, while population exposure in very high-risk zones peaks mid-century before declining under most SSPs, except SSP3-7.0 where it rises monotonically. These findings underscore the critical need for pathway-specific adaptation strategies to mitigate escalating flood impacts in an increasingly polarized risk landscape.